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Friday, May 22, 2015

Lightning Fest Starts the Memorial Day Weekend

Nature is supplying its own fireworks to signal the Memorial Day weekend. For the past several days, large numbers of thunderstorms have moved westward across eastern Oregon and Washington, while others have developed over the Cascades and Olympics.

To illustrate, here is summary of the lightning strikes for Thursday. Eastern Oregon, Idaho, and the Washington Cascades were covered by lightning.

A particularly strong thunderstorm cell hit Yakima Thursday evening, which received about an inch of rain within an hour. The radar at 7:50 PM Thursday shows the heavy rain (red colors)

And localized flooding was observed around the area.

A lot more action occurred today (Friday), with a squall line of thunderstorms moving across eastern Washington, with heavy rain and gusty winds. The radar at 7 PM this evening shows the action (red is the heaviest rain or hail):

And, of course, this heavy rain was associated with lots of lightning. We are fortunate that all this is happening early in the summer, with the ground moist enough so that the lightning is not initiating fires. The story will be different in two months.

The configuration of unusually persistent easterly flow and lots of thunderstorm east of the Cascade crest, which has held in place over the past week or two, may be the result of the strong El Nino that is developing. My colleague, Nick Bond, who is also State Climatologist, examined the relationship between El Nino and regional precipitation (see the figure below, which shows the correlation between El Nino and precipitation for the month of May). Eastern WA and Oregon are wetter than normal, while western WA is drier than normal--EXACTLY what has happened.

The million dollar question all of you are asking is what this weekend will be like. Will the Folklife Festival be a rain out? Will you get wet hiking in the Cascades?

Actually, it doesn't look that bad. Here is the total precipitation for the next 72 hr starting 5 AM Saturday. Relatively dry for most of western Oregon and Washington, with the major exception being light showers in the Cascades. Much wetter over the Rockies and Nevada.

We do have marine air pushing in west of the Cascades, so no heat waves are ahead. Highs in the mid-60s and considerable clouds over the lowlands.